Known wind turbines, which provide a maximum power output of for instance 2.3 MW or 3.6 MW, comprise a nacelle respectively a nacelle canopy, which is typically made out of steel. Since steel is a stable material with a high electric conductivity the canopy is able to take and to sustain direct lightning strikes. Thereby, the canopy forms a Faraday cage, which surrounds (a) system components of the respective wind turbine and (b) people being situated inside the nacelle for instance in order to perform maintenance tasks.
A new generation of wind turbines will be equipped with a nacelle respectively with a nacelle canopy, which is made from a non-conductive material. Specifically, the canopy for a nacelle of a new type of wind turbine will be made from a non-metallic material such as for instance a glass fiber reinforced plastic.
In order to allow for a good shielding with respect to electromagnetic compatibility (EMC) the inside of a glass fiber canopy may be covered with a thin metal coating such as for instance a metallic paint. However, such a coating is typically not able to withstand or to handle currents, which are caused by a lightning stroke and which may have a peak current amperage up to 200 kA, as requested for lightning protection level 1 (see “Technical Report IEC 61400-24, Wind Turbine generator systems, Part 24: Lightning Protection”). Therefore, additional down-conductors will be necessary which electrically connect protective lightning rods, which are located atop the cooler and the generator of the wind turbine, to the bedplate of the nacelle. However, in case of a direct lightning such a down-conductor will have to carry a high lightning current through the inside of the nacelle. The resulting electromagnetic fields may harm electrically sensitive system components, which are located within the nacelle. Therefore, a lightning protection zone 2 (LPZ2) cannot be realized by using standard down-conductors from the lightning rods to the bedplate of the nacelle.
There may be a need for improving the lightning protection of a nacelle having a non-metal canopy.